In general, insulation of high-voltage junctions in cathode-ray tubes employed in television sets and other devices is attained by a method in which, as shown in the Drawing, a silicone grease 8 is applied to the interface between an anode cap 5 made of silicone rubber and a cathode-ray tube 1 to thereby prevent moisture infiltration and maintain good electrical insulation.
However, conventional silicone greases have had a problem that since they show good compatibility with silicone rubbers constituting the anode caps, silicone oils contained in the silicone greases penetrate into the silicone rubbers to swell the rubbers and, as a result, sealing of the high-voltage junctions is impaired. Hence, there has been proposed a method for suppressing the compatibility with silicone rubbers by increasing the molecular weight of silicone oils which are base oils of the silicone greases as disclosed in, for example, JP-B-U-53-52376. (The term "JP-B-U" as used herein means an "examined Japanese utility model publication".)
Further, in view of the fact that a silicone grease based on a methyl alkyl silicone oil containing an alkyl group other than methyl shows low compatibility with a dimethyl silicone rubber, thus reducing swelling of the rubber, such silicone grease has been used.
On the other hand, since television sets recently have frequently caused fires, there is a growing trend toward use of flame-retardant materials for parts of television sets. For example, a flame-retardant grease comprising a vinyl group-containing silicone oil and a platinum compound is known as a silicone grease for a cable filler as disclosed in, for example, JP-A-63-235398. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) Further, the silicone greases used for the electrical insulation and moistureproof sealing of anode caps also have been required to have the flame-retardant properties. Therefore, development of a silicone grease having reduced swelling properties to the silicone rubbers and good flame retardant properties is demanded.